1. Field of the Invention
The invention relates to a demolition hammer and/or hammer drill in accordance with the preamble of claim 1.
2. Description of the Related Art
When working with demolition hammers and hammer drills it is frequently the case that the tool, e.g. a chisel or a drilling tool, becomes fixedly wedged or jammed in the rock. Whilst, after gaining some practice at drilling using the hammer drill, it is still possible in most cases to prevent the tool from becoming jammed, during demolition work using a large demolition hammer it is not always possible even for the person skilled in the art to prevent the chisel from becoming wedged or jammed.
This has been remedied by means of a percussion device which is disclosed in DE 197 31 732 A1. If the tool becomes jammed, the person operating the demolition hammer or hammer drill is able to switch on a free percussion device which serves to deflect the drive force, so that it influences the tool in the opposite direction to the main percussion direction, whereby—as tests have shown—the jammed tool can be released with a small number of impacts.
In the case of the known percussion device, a push lever is to be actuated on each occasion by the operator when the tool becomes jammed, whereby a percussion changing device can be activated. Furthermore, difficulties are to be expected in the sealing arrangement.